Both private and public distribution lists can be expanded.
An error will occur if the EmailAddress that is specified in the request does not correspond to a distribution list, or if the ItemId that is specified in the request corresponds to a non-private distribution list.
// Create an ExpandDLType.
ExpandDLType expandDl = new ExpandDLType();
// Set the e-mail address and routing type of the distribution list.
expandDl.Mailbox = new EmailAddressType();
expandDl.Mailbox.EmailAddress = "myDL@myDomain.com";
// Expand the distribution list.
ExpandDLResponseType expandDlResponse = esb.ExpandDL(expandDl);